Since your plan is to add RO water, you are going to need to add some minerals back in there to buffer the water a bit. CO2 is acidic and will drive the pH of water down. Many of us use tap water, or mix with tap water to retain some of the hardness. Your plants will also benifit for the calcium and magnesium that you are stripping out with your RO filter. I would aim for a dKH of 3-7.

thanks digger. i already added tap water to the RO water. i did a 60/40 mix. i'll test the dKH once im ready to put something in there. seems like the only thing i'll have in there for a while is the substrate and the driftwood. just not happy with the aquascaping so far.